1. Field of the Invention
This invention relates to an improved collection tank for the in situ collection of waste grease such as cooking oils or grease, and to a method of collecting the grease by elevating the tank and lowering it into a hot water bath to warm the walls and facilitate dumping of the grease.
2. Description of the Prior Art
It is well known to collect used or waste greases in collection or holding tanks at the point of use such as at a fast food restaurant or the like, then to collect the waste grease from such tanks for processing and/or recycling. U.S. Pat. No. 4,450,828 and U.S. Pat. No. 5,718,220 disclose waste grease tanks used for collecting grease products, and a process for collecting the grease by a transport truck including a heating bath for heating the tank so that the grease can be easily dumped.
With reference to FIG. 4, which is a copy of FIG. 1 found in U.S. Pat. No. 4,450,828, the numeral 11 generally designates a truck, which has conventional wheels 13 and a cab 15 associated with a conventional engine (not shown). The cargo part 17 is a large tank for holding the dumped grease. In the bottom of the tank 17 there is a tube by which steam can be fed through in-out openings 20 to melt the collected grease from drainage (at a warehouse) through a valved outlet coupler 21.
The mechanism for lifting, immersing, and dumping the containers comprises a pair of lever arms 24 simultaneously swung by hydraulic cylinders 26. The upper ends of the arms 24 are bridged by a bar and by a shaft having winch spools 29 thereon for winding and unwinding cables or chains 31 thereon. The winch 29 is opened by a reversible hydraulic motor 33 of know construction.
The on-site left-there container 35 is of a size of equal several of the barrels previously employed. It has downwardly inwardly tapered sides to facilitate dumping the semi-sold grease block after its sides are heat-softened by immersion of the container in a hot-water-bath vat located, for example, at the rear of the truck (heated in known manner by an immersion electric heater or by hot-water or exhaust-gas coils, not shown). The container 35 has lift lugs 39 and dumping-tilting lugs 40.
The grease-dumping operation is best illustrated in FIG. 4. Firstly the container is sitting at ground level (left phantom). Secondly, it is winch-lifted to the full-line-shown position. Thirdly, it is lowered into the hot-water bath at the rear of the truck. Fourthly, it is again lifted and is swung to the last (right) position shown in FIG. 4. Fifthly, it is dumped by lowering the container 35, so that the lugs 40 enter J-shaped pockets 53, which are welded to the inner faces of the lift levers 24. After this, further lowering of the container 35 makes it pivot around said lugs 40 to dump its grease contents.
Under certain conditions, environmental protection considerations now require waste grease collection tanks to have double walls to guard against spillage or leakage in the event of an accidental rupturing or puncturing of the tank wall. However, such double-walled construction provides an insulating air space between the inner and outer container walls which makes submergence into a hot water bath particularly ineffective in warming the inner container wall to facilitate dumping of the solid or semi-solid waste grease.
It is therefore an object of the present invention to provide an improved double-walled collection tank which facilitates emptying of waste grease from the tank.
It is another object to provide a double-walled collection tank which may be quickly and effectively heated by dipping into a hot water bath to facilitate emptying of the solid or semi-solid grease stored therein.
Another object is to provide an improved method of emptying solid or semi-solid waste grease from a double-walled collection tank.